Quantum Dot (QD) is a nano-semiconductor structure which binds conduction band electrons, valence band holes and excitons in three directions, also called nanocrystalline, i.e. a kind of nano-particles composed of II-VI group elements or III-V group elements. The particle sizes of the quantum dots are generally between 1 nm to 10 nm, and due to the quantum confinement of the electrons and the holes, the continuous band structure becomes a discrete level structure having a molecular characteristic and can be excited to emit fluorescence. The CSP (Chip Scale Package, chip level package) LED as a stand-less LED has become an important development objective of the LED for now due to its simple manufacturing process, heat dissipation, small light emitting surface and other advantages.
FIG. 1 is an absorption spectrum of red quantum dots and green quantum dots. FIG. 2 is an emission spectrum of red quantum dots and green quantum dots. In FIG. 1 and FIG. 2, the gray line represents the green light quantum dot and the black line represents the red light quantum dot. As shown in FIG. 2, the full widths at half maximum (FWHM) of the red quantum dots and the green quantum dots are very narrow. Therefore, adding quantum dots to the light source can greatly improve the color gamut of the liquid crystal display.
However, the luminous efficiency of the quantum dots gets lower due to the severe temperature quenching and temperature rising. Besides, in case that the quantum dots are exposed to a water and oxygen environment, there is an irreversible and rapid decline in the fluorescence efficiency. Therefore, the quantum dots need to be isolated from the water and oxygen environment, isolated from high temperatures, or provided with a good heat dissipation environment.